The railway block signalling bell code is a system of bell sounds used in
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
to communicate between manually operated
Signal Boxes
On a rail transport system, signalling control is the process by which control is exercised over train movements by way of railway signals and block systems to ensure that trains operate safely, over the correct route and to the proper timetab ...
in implementing the railway
block system. (The bell system is not used in modern power signal boxes, other than to any older adjacent signalboxes.) Each such signal box has a bell circuit to the boxes on either side of it along the line. The equipment consists of a plunger or tapper (rather like a
Morse key) which when pressed, rings a
single-stroke bell in a neighbouring box. That box similarly has a tapper for communicating back, so boxes have keys each of which rings the bell in a neighbouring box. The bells sound different tones, so that the
signalman
A signalman is a person who historically made signals using flags and light. In modern times, the role of signalmen has evolved and now usually uses electronic communication equipment. Signalmen usually work in rail transport networks, armed for ...
can tell them apart by ear.
Examples
Although codes varied from region to region, the following shows a few selected standard UK bell codes:
["BR Regulations for Train Signalling 1st Oct 1960"]
Typical use
These would be used as follows (assuming a simple exchange between two signal boxes on a plain section of line) between two signal boxes A and B. Assume a train is to pass from the block controlled by A to the block controlled by B. This must be agreed and permitted by the signalman in box B. Here is the sequence of bell codes and associated actions:
# Box A sends 1 bell to box B. (Call attention.)
# Box B replies with 1 bell to box A. (Acknowledgement, indicating readiness.)
# Box A sends 4 bells to box B. (Is line clear for express passenger train?)
# Box B sends 4 bells to box A. (Acknowledgement, if in the position to accept the train giving permission for box A to signal the train into the block controlled by B.)
# (when the signalled train enters the portion of line between A and B.) Box A sends 2 bells to box B. (Train entering section.) This is sent as the train passes box A and enters the block controlled by B.
# Box B sends 2 - 1 bells to box A. (Only after confirming that the train has arrived complete and no portion of it remains within the block section between A and B or the clearing point for that section. This could be done by the guard of the train notifying the signalman or by the signalman observing the tail-lamp.)
See also
*
Bell codes are used on multiple unit trains for communication between drivers and guards, but are not the codes listed above.
*
Whistle code
A train whistle or air whistle (originally referred to as a steam trumpet) is an audible signaling device on a steam locomotive, used to warn that the train is approaching, and to communicate with rail workers. Modern diesel and electric locomot ...
s are used by railway engines to communicate with signal boxes and other staff.
References
Information about "standard" UK bell codes and variations on www.signalbox.org
Railway signalling block systems
{{UK-rail-transport-stub